To adapt the position of the steering wheel in motor vehicles to the different ergonomic requirements of different users, steering columns are designed to be adjustable. In general, adjustable steering columns can be adjusted in a vertical direction and in a longitudinal direction of the motor vehicle. Here, a distinction can be made between a locked setting of the steering column, for the normal operation of the motor vehicle, and an unlocked setting, for the adjustment of the position of the steering column. In the locked setting, the steering column is fixed relative to the chassis of the motor vehicle. Here, the fixing of the steering column is selected such that the steering column withstands even the high loads that arise in the event of a crash, or permits a controlled dissipation of crash energy. At the same time, such fixings should, in the unlocked setting, permit easy manual adjustment of the steering column.
The adjustability of steering columns is generally made possible by way of variable positioning of a guide box, in which a steering spindle is received, relative to a bracket for the attachment to the chassis of the motor vehicle. In the case of the known solutions, a distinction is made here between force-fitting and form-fitting connections between guide box and bracket.
A form-fitting connection is known for example from DE 10 2011 000 319 B3. In the case of said form-fitting connections, there is the problem that the components involved in the form fit are also plastically deformed every time the steering column is locked. As a result, the components of the steering column that provide the contact are subject to considerable mechanical wear.
The locking systems based on a force-fitting connection permit locking of the steering column generally by way of the elastic deformation of the bracket. Locking based on a force fit is known for example from US 2008/0252056 A1. A disadvantage of said force-fitting connections is that, to provide the force fit, it is always necessary for one or more parts of the bracket to be of elastic form. This has the result that characteristics of the bracket, such as the rigidity thereof and the natural frequency thereof, are determined by the requirement for elasticity. Specifically with regard to the crash situation, however, high levels of rigidity of the bracket as an attachment point of the steering column to the chassis are desired. Furthermore, against the background of vibrations originating from the engine and from the roadway, high demands are placed on the natural frequency of the structural components of the steering column, and as high a natural frequency of the vibratory system as possible is desired.